Create read only handles for empty_array and sentinel objects

vm/code_descriptors_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/assert.h"
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64)
 
 #include "vm/ast.h"
 #include "vm/assembler.h"
@@ skipping 259 matching lines @@
   // We can't easily check that we put the stackmap at the correct pc, but
   // we did if there was exactly one call seen.
   EXPECT(call_count == 1);
   const Array& stack_maps =
       Array::Handle(stackmap_table_builder->FinalizeStackmaps(code));
   code.set_stackmaps(stack_maps);
 
   // Now invoke 'A.moo' and it will trigger a GC when the native function
   // is called, this should then cause the stack map of function 'A.foo'
   // to be traversed and the appropriate objects visited.
-  const Array& args = Array::Handle(Object::empty_array());
-  const Object& result = Object::Handle(DartEntry::InvokeStatic(function_foo,
-                                                                args));
+  const Object& result = Object::Handle(
+      DartEntry::InvokeStatic(function_foo, Object::empty_array()));
   EXPECT(!result.IsError());
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32 || defined(TARGET_ARCH_X64)